Abstract
Alternatives to synthetic chemicals are undertaken against phytopathogens. The aim of this work is to evaluate the effect of seed extracts of Thevetia peruviana (Pers.) K. Schum. on Mycosphaerella fijiensis Morelet, fungus responsible for banana black leaf streak disease. Five extracts of T. peruviana, hexane extract (HE), ethyl acetate extract (EAE), acetone extract (AcE), methanol extract (ME) and aqueous extract (AqE), and a fungicide, Azoxystrobin were used. GC-MS of acetone extract was performed. Fifty (50) strains of M. fijiensis per sampling site were tested. Three concentrations of extracts 6.25 (C1), 12.5 (C2), and 25 (C3) μl/ml, a negative control (0 μl/ml) and 10 ppm of azoxystrobin were used for the tests. The MIC50 and MIC90 were determined. GC-MS showed chemical compounds with different molecular height such as acids, sugars, and esters. AcE and AqE significantly reduced M. fijiensis germ tube growth at C2 and C3 concentrations and with inhibition percentage respectively ranged of 60-90% and 40-80%. The growth levels of the germ tubes were above the strobilurin resistance threshold at Njombe and peasant plantation, ranging from 77.9% to 92.3%. AcE showed the same or superior efficacy as the fungicide used on conidial germination at all tested concentrations. The MIC50 totally reducing mycelial growth and conidial germination was 6.25 μl/ml. T. peruviana seeds extracts can be exploited in integrated pests management against M. fijiensis.
Highlights
Fungi are responsible for almpost 60% of crop diseases (Lepoivre, 2003)
acetone extract (AcE) and aqueous extract (AqE) significantly reduced M. fijiensis germ tube growth at C2 and C3 concentrations and with inhibition percentage respectively ranged of 60-90% and 40-80%
In Cameroon, Mycosphaerella fijiensis Morelet, a fungus belonging to Ascomycetes is responsible for the black leaf streak disease (BLSD)of plantain and sweet banana (Musa sp)
Summary
Fungi are responsible for almpost 60% of crop diseases (Lepoivre, 2003). Their fructifications are the source of primary inoculum in farms. Banana, which is ranked fourth among agricultural products after rice, wheat and maize, is the most popular fruit on the planet (Lescot, 2006; Lassoudière 2010) This very important sector for Cameroon (first African banana producer), contributes approximately 7% of primary GDP (Gross Domestic Product) and is the second largest national employer after the government and the second largest source of income after timber (Mouliom et al, 1997; Ngando et al, 2006). In most banana production areas, black leaf streak disease is the greatest threat (De Lapeyre et al, 2010) This disease caused by M. fijiensis affects the photosynthesis of bananas through partial or total drying of the foliar system of the plant (Mourichon, 2003). This results in yield losses of up to 100% (Hermento et al, 2010), the reduction of the green lifespan of fruits, making their transport and conservation problematic (Churchill, 2011)
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